1. Field of the Invention
The present invention relates to a data processing circuit for a disc player designed for playback of a digital audio disc known as a compact disc (CD) and, more particularly, to a reproduced data processing circuit adapted for use in a shock-proof CD player contrived to solve a problem of track jump caused by shock.
2. Description of the Related Art
In the conventional shock-proof CD players known heretofore, it has been generally customary that, upon occurrence of a track jump due to some shock or the like in a playback mode, a pickup device is returned to the position immediately before occurrence of such track jump, and the playback operation is started again from that position. Then the PCM audio data reproduced after resumption of the playback operation is linked, by the use of a great-capacity RAM, to the reproduced PCM audio data obtained immediately after such track jump, whereby the prerecorded music or the like can be reproduced continuously without any intermission.
However, any of the CDs available at present has merely a subcode utilizable as an information index. Therefore, when a linking process is executed for the PCM audio data in response to a track jump in a shock-proof CD player, there is used a Q-channel time code in such subcode.
The subcode data can be reproduced immediately after eight-to-fourteen modulation (EFM). And since a deinterleaving process is not necessary, a time base correction (TBC) is not executed.
Meanwhile with regard to the reproduced PCM audio data, a time base correction is executed to reduce the wow and flutter derived from the rotation jitters and so forth of a CD driving motor. Therefore it is impossible to settle the positional relationship on the time base between the pre-TBC subcode data and the post-TBC PCM audio data, so that a decision is not exactly attainable as to when the latest reproduced audio information is outputted after the time base correction, whereby the joint of the PCM audio data is not detectable.
For the reason mentioned above, it is usual in the related art to execute the linking process by detecting several points where the PCM audio data are successively coincident.
However, in the method that detects several points of successive coincidence of the PCM audio data, there arise some problems including that, if any error exists in the PCM audio data, it becomes impossible to execute the proper linking process for the PCM audio data, and mislinking is prone to be induced in the case of no sound or a periodic signal of a fixed value to consequently deteriorate the operational reliability.